Federal officials have quietly introduced new guidelines that make it tougher for asylum seekers to get their cases heard before judges.

The U.S. Citizenship and Immigration Services sent a memorandum to asylum office directors and deputy directors on Feb. 28 describing “major changes” in the standards for asylum seekers who make “credible fear of persecution” claims.

In the memo, John Lafferty, the chief of the asylum division, highlighted concerns that previous standards had been wrongly interpreted to require only a “minimal” or “mere possibility” of success in court.

Credible-fear referrals rose by more than 250 percent from fiscal year 2012 to 2013, he wrote.

The revised guidelines seek to clarify that the standards require the applicant to “demonstrate a substantial and realistic possibility of succeeding,” Lafferty wrote.

Requests for comment from immigration officials went unanswered Friday.

Bill Hing, a political asylum expert and law professor at University of San Francisco, said the new guidelines imposed a burden that surpassed well-founded fear standards established by the Supreme Court.

“I think they’ve created an atmosphere or they’ve sent a message to the asylum officers, not only is this is serious, but the applicant has this huge hurdle to satisfy,” Hing said. “That’s the wrong message. That isn’t what was intended by Congress.”

Hing was co-counsel in the Supreme Court case INS v. Cardoza-Fonseca, which ruled in favor of more lenient standards.

In its opinion, the high court wrote: “So long as an objective situation is established by the evidence, it need not be shown that the situation will probably result in persecution, but it is enough that persecution is a reasonable possibility.”

The National Immigrant Youth Alliance, an advocacy group, released the memo to the news media Thursday afternoon. The alliance has helped lead several protests at border crossings. Last year, it assisted groups of Mexican nationals who sought to cross back over the U.S. border and seek asylum. One group of nine young immigrants, known as the “Dream 9,” have been allowed to remain in the United States while they wait for a hearing after an asylum officer found they had credible fear of persecution or torture in their birth country.

But David Bennion, a Philadelphia-based lawyer who’s worked with the immigrant youth alliance, said other clients of his had been denied the opportunity to see judges since the new guidelines were introduced. One client, he said, was a pregnant victim of domestic violence who was fleeing her attacker.

“It should be a no-brainer for credible fear, but it was denied,” he said.